Verify that the fasteners are tight. I have an FCM set that had a loose nut holding the damper up top (from FCM). It made a lot of noise on the significant bumps but was quiet otherwise just like a set of coil overs I had on another car so I thought it was normal. Over time the nuts loosened and one popped off at Shenandoah. FCM made right by sending replacement parts. I tightened the crap out of those nuts and it has been fine for 10k+ miles since. The nuts did not seem loose and I have had other cases in which fasteners seems tight but were not and caused a heck of a noise.
Also, unless you recently changed something to suspect that, it could be a worn component, like the end links, that have no relation to your Billies.

 

Good call. I've got a set of 949 extended tophats I need to put on, I'll torque the **** out of everything when I put it back together.

 

It's hard to properly torque the top nuts since the shock shaft tends to rotate, I've never tried to use the allen key in the shaft, most are usually stripped. I find the best way is to use the impact gun and torque to TWO ugga duggas, then use a second nut to prevent loosening. Never had one loosen up on me.

 

I've never had a top hat that didn't have two nuts on it. You don't have to overtighten them if you have a locking nut.

Do all of them not have locking nuts? o_O

 

All mine are on with single nylock nuts.

 

OEM NB shocks come with the two nut setup which is what I use exclusively.

 

Yeah, that's what I'm using as well, tightened with an impact

 

Could be your top hat...

 

I don't think it's your suspension at all. I think it's your exhaust.

 

Mine have only ever had nylocs NB billies or xidas. I just impact gun them until the rubber bushings start to compress a little. If the battery was low on my old HF impact and it did not spin fast enough I'd just vise grip the bump stop to hold the shock enough but also not mar it.

 

calteg, It could be a million things. I thought after my post that I should have said: get under there and fiddle with everything starting in the area that seems like the source. Unless it is obvious when you grab it, it could take a lot of trial and error. If you recently changed something and the sound started with the change, start there.

FCM used a single custom nut when I got my set back around 2008. 5XRacing offers a similar set up.

 

I've seen shocks that just used a single nylock nut on the top.

 

That's for NA hats. I don't mess with them, so i suppose that would probably explain it. :P

 

FWIW, new bilsteins come with a single nylock nut. All my setups use the supplied single nut.

 

My Tiens had a single nut for the top but it was the locking style (not nylock) and the Fox I just put in have the 2 nuts. I hand tightened the first one until the bushing compressed which is just about where the shaft starts to rotate and then hand tightened the 2nd nut on top of it. Directions say only 10 ft-lbs. so not a lot of force needs to be applied.

 

Did you tighten the shock top nuts with the suspension on the car?

I've seen them be tight when assembling them, but loose after everything's on the car more than once.

 

Jesus Christ, are you guys still talking about your nuts? This is how stereo types get started for miata owners.

 

I did not, though I'm 90% sure the noise is my golf cart battery that I wedged into the stock battery tray.

 

Greetings all; glad to have found this thread as I'm putting together a NB coil over. I'm gathering parts and I have two questions. First, which coil sleeve setup is/works better; Allstar or 5XRacing, something else? I won't be using extended top hats so not having to cut the sleeves would be nice, and a nice tight fit on NB shocks is also preferable.

Next, I've read here or elsewhere that the OEM NB lower bushing washer doesn't fit within 2.5" springs; is it a close fit I can easily chuck up on a lathe and cut down, or is it just way too big?

 

If you have access to a lathe you can cut eBay sleeves to capture the circlip, machine the cup washer to clear the spring and depending on the spring you run cut new grooves in the shocks too lower the sleeves